Taras Radchenko

National Academy of Sciences of Ukraine | ISP · G. V. Kurdyumov Institute for Metal Physics

The paper combines two theoretical approaches – the method of grazing dynamical diffraction (which allows performing the nondestructive structural diagnostics of defects in the near‐surface layers) with efficient numerical simulation method (which enables computation of electron structure in realistically large systems with millions of atoms) – for...

The chapter generalizes results on influence of external strain or/and magnetic fields on the electronic and transport properties of graphene with different kinds of imperfections (point defects, etc.): resonant (neutral) adsorbed atoms either oxygen-or hydrogen-containing molecules or functional groups, vacancies or their complexes with substituti...

Harnessing the full potential of graphene for optoelectronic and electrochemical devices requires tunning and goal-directed control of its electronic properties. We report a computational study of the electron density of states and catalytic activity of graphene in the perpendicular magnetic field. We focus on the influence of uniaxial strain, cova...

We study numerically a role of the uniaxial tensile strains and disordered defects in their impact on electronic density of states (DOS) in graphene exposed to an external magnetic field. The DOS curves are calculated using the tight-binding Hamiltonian, where the perpendicular magnetic field and uniaxial tension are included via the relevant modif...

We study the processes of dynamical diffraction of the plane X-ray waves on the graphene film/SiC substrate system in the case of the Bragg diffraction geometry. The statistical dynamical theory of X-ray diffraction in imperfect crystals is applied to the case of real quasi-two-dimensional systems. The necessity of the taking into account of the va...

We study the effects of the uniaxial tensile strain and shear deformation as well as their combinations on the electronic properties of single-layer black phosphorene. The evolutions of the strain-dependent band gap are obtained using the numerical calculations within the tight-binding (TB) model as well as the first-principles (DFT) simulations an...

We study the effects of the uniaxial tensile strain and shear deformation as well as their combinations on the electronic properties of single-layer black phosphorene. The evolutions of the strain-dependent band gap are obtained using the numerical calculations within the tight-binding (TB) model as well as the first-principles (DFT) simulations an...

We study the processes of dynamical diffraction on the graphene film/SiC substrate system. The statistical dynamical theory of X-ray diffraction in imperfect crystals is extended to the case of real quasi-two-dimensional systems. The necessity of the taking into account of the variability of the lattice parameter of multilayer graphene, as well as...

An object of the study in the chapter is the α″-Fe16N2-type phase, which possesses unique and promising magnetic properties, does not contain critical (non-renewable on the earth) elements, and that is why it stands as an alternative to both bulk and nanoscale rare-earth permanent magnets. The ferromagnetic α″-Fe16N2 martensite is nanostructured, i...

Among the family of currently known promising quasi-two-dimensional (2D) materials, the authors of this survey concentrate on the problem of functionalization of the graphene- and phosphorene-based structures. In most cases, the modification of their properties occurs through the covalent or noncovalent surface functionalization and mechanical affe...

We show abrupt changes in the electronic properties of graphene with different types of binding to oxygen. Whereas oxygen bonded to the basal plane in the form of functional groups p-type dopes graphene, we prove that substitutional (i.e. in-plane) oxygen n-type dopes it. Moreover, we determine that impurity scattering potentials introduced by thes...

We report on the results obtained modelling the electronic and transport properties of single-layer graphene subjected to mechanical or magnetic fields and containing point defects. Reviewing, analyzing, and generalizing our findings, we claim that effects of uniaxial tensile strain or shear deformation along with their combination as well as struc...

Для з’ясування основних рис симетрійно-енергетичного та структурно-ентропійного аспектів взаємочину домішки та розчинника розвинуто конфіґураційний модель бездифузійного утворення «гібридного» твердого розчину втілення–заміщення Me–X, в якому взаємодійні атоми неметалу X можуть займати як октаедричні міжвузловини, так і вузли ОЦК(Т)-ґратниці металу...

Implementing the quantum-mechanical Kubo-Greenwood formalism for the numerical calculation of dc conductivity, we demonstrate that the electron transport properties of a graphene layer can be tailored through the combined effect of defects (point and line scatterers) and strains (uniaxial tension and shear), which are commonly present in a graphene...

The literature (experimental and theoretical) data on the tetragonality of martensite with interstitial–substitutional alloying elements and vacancies are reviewed and analysed. Special attention is paid to the studying the martensitic αʺ-Fe16N2-type phase with unique and promising magnetic properties as an alternative to the rare-earth intermetall...

The possibility of inducing a sizeable energy gap in the electronic structure of a graphene layer is still one of the biggest and most debated challenges in graphene electronics. Despite promising theoretical results, some experimental studies report the absence of a band gap even in highly mechanically strained graphene. In this paper, we address...

This chapter generalizes results on the influence of uniaxial strain and adsorption on the electron states and charge transport or localization in graphene with different configurations of imperfections (point defects): resonant (neutral) adsorbed atoms, either oxygen- or hydrogen-containing molecules or functional groups, vacancies or substitution...

We report a calculational study of electron states and the resulting electrochemical properties of uniaxially strained graphene with point defects. For this study the reduction of ferricyanide to ferrocyanide serves as a benchmark electrochemical reaction. We find that the heterogeneous electron transfer activity of the perfect graphene electrode r...

The main goal of our study was investigation of the influence of the deformations (sufficiently large for the establishing the non-zero gap) on electrotransport properties of impure graphene. To achieve this purpose, we implemented the simulation package that allows to perform numerical calculation of the conductivity and mobility of graphene sampl...

The study deals with electronic properties of uniaxially stressed mono- and multi-layer graphene sheets with various kinds of imperfection: point defects modelled as resonant (neutral) adsorbed atoms or molecules, vacancies, charged impurities, and local distortions. The presence of randomly distributed defects in a strained graphene counteract the...

The theoretical propositions as well as corresponding outputs and conclusions based on 30 scientific works, where the theory of ordering of crystal structures with point or/and line defects is developed, are presented to be defended. The defect-structure ordering is considered as being intermediate mechanism in affecting the properties of mixed cry...

As revealed, with the change of random spatial distribution of adatoms all over the graphene layer for correlated and ordered ones, the electroconductivity enhances in several (tens) times. Randomly arranged adatoms, which are attractive for uncombined charge carriers, manifest themselves as the long-range scattering centres, while they dominate as...

The chapter combines analytical (statistical-thermodynamic and kinetic) with numerical (Kubo-Greenwood-formalism-based) approaches used to ascertain an influence of the configurations of point (impurities, vacancies) and line (grain boundaries, atomic steps) defects on the charge transport in graphene. Possible substitutional and interstitial graph...

The chapter combines analytical (statistical-thermodynamic and kinetic) with numerical (Kubo-Greenwood-formalism-based) approaches used to ascertain an influence of the configurations of point (impurities, vacancies) and line (grain boundaries, atomic steps) defects on the charge transport in graphene. Possible substitutional and interstitial graph...

Charge carrier transport in single-layer graphene with one-dimensional charged defects is studied theoretically. Extended charged defects, considered an important factor for mobility degradation in chemically-vapor-deposited graphene, are described by a self-consistent Thomas-Fermi potential. A numerical study of electronic transport is performed b...

Using the ab initio methods, boron or nitrogen doping effects on the characteristics of electron and vibrational spectrums of graphene are studied. We revealed that a mutual arrangement at the largest distance from each other is energy-preferred for these dopant atoms. Depending on their kind, one can regulate conductance and raise values of fundam...

Possible ordered distributions of carbon (C) and substituting dopant (A) atoms over the sites in a graphene-type lattice are considered for C2A- and C5A-type (super)structures (corresponding to stoichiometries of 1/3 and 1/6, respectively). Relaxation model of atomic long-range order (LRO) in a graphene-based lattice is developed, and kinetic curve...

Exact numerical calculations of the conductivity of graphene sheets with random and correlated distributions of disorders have been performed using the time-dependent real-space Kubo formalism. The disorder was modeled by the long-range Gaussian potential describing screened charged impurities and by the short-range potential describing neutral ada...

The interatomic-interaction energies are calculated, and the spatial distributions of B or N impurity atoms in graphene lattice are predicted, using density functional theory and statistical-thermodynamic model, respectively. At least, at low temperatures, calculated energy parameters correspond to formation of stabile graphene-based CBc and CNc su...

The statistical thermodynamics of a binary honeycomb-lattice gas is studied. The possible ordered distributions of substitutional atoms over the sites are predicted and a problem of their stability is analyzed. The ranges of values of interatomic-interaction parameters providing the low-temperature stability of the honeycomb-lattice-based superstru...

The literary data on the structure, basic methods of fabrication, mechanical and electrical properties of nitrogen containing carbon nanotubes (N–CNT), which make possible its use in a nanotechnology, are summarized. Depending on the N–CNT configuration their thermodynamic stability is studied using the molecular dynamics and Monte-Carlo methods. P...

Using the statistical-thermodynamic methods within the scope of the self-consistent field approximation, an atomic ordering of the substitutional b.c.c.-Fe-Co alloy and the magnetic contribution of both its components (Fe and Co) in the interatomic interaction are investigated, and the temperature-concentration dependences of atomic order and magne...

Ordered distributions of carbon and substitutional dopant (A) atoms over the sites of a graphene lattice, i.e. CmA superstructures with dopant contents c=1/(m+1), and problem of their stability are considered theoretically. The ranges of values of interatomic-interaction parameters providing the low-temperature stability of the graphene-based C7A,...

The literary data on the structure, basic methods of fabrication and treat-ment as well as physical properties of graphene, including a doped one, which enable use of it as a functional nanomaterial, are reviewed. Ordered distributions of substitutional atoms over the sites of a two-dimensional honeycomb lattice at different compositions and temper...

Possible stably ordered substitutional structures based on a graphene-type crystal lattice are considered. A kinetic model of atomic ordering in metal-doped graphene with stoichiometric (1/8, 1/4, 1/2) and nonstoichiometric compositions is developed. Inasmuch as the intrasublattice and intersublattice ‘interchange’ (‘mixing’) energies are competiti...

The statistical-thermodynamics and kinetics models of atomic order in interstitial solution based on a two-dimensional graphene lattice (C–X) are proposed. Ordered distributions of interstitial atoms (X) over the interstices of the honeycomb lattice at the different compositions and temperatures are described theoretically. The ranges of values of...

Using the statistical-thermodynamic methods within the scope of the self-consistent field approximation, an atomic ordering of the substitutional b.c.c.-Fe–Co alloy and the magnetic contribution of both its components (Fe and Co) in the interatomic interaction are investigated, and the temperature-concentration dependences of atomic order and magne...

The statistical-thermodynamics and kinetics models of atomic ordering in a metal-doped graphene (binary two-dimensional planar graphene-type crystal lattice) at 1/8, 1/4, and 1/2 stoichiometries are proposed. Impossibility of (completely) atomic-ordered distribution at 1/6 and 1/3 stoichiometries is ascertained in a graphene-type crystal lattice (i...

The statistical-thermodynamic model of atomic ordering into L12 or D019 structures in alloys under pressure, p, with the volumes feebly depending on the long-range order parameter and a composition is considered. Pressure raises or reduces Kurnakov’s temperature (Tk) depending on signs of energy parameters of interatomic interactions (within the sc...

Within the framework of the lattice-statics and static fluctuation-waves’ methods, the available energies of strain-induced interaction of interstitial–interstitial, interstitial–substitutional and substitutional–substitutional impurity atomic pairs are collected and analysed for f.c.c.-(Ni,Fe)–C solutions allowing for discrete atomic structure of...

Using the Onsager-type kinetics equation, the differential equation for the kinetics of orientational long-range order (LRO) parameter for the interstitial H-atoms' distribution within the hexagonal close-packed (h.c.p.) lattice of a metal (Me) is firstly derived. The numerical solutions of this equation enable to analyze the orientational ordering...

Models of statistical thermodynamics and kinetics of ordering of alloying atoms in graphene into substitutional C(1-с)–Me(с) superstructures with the selected stoichiometries (c = 1/8, 1/4, 1/2) are considered. Results are the evidence of possible nonmonotony of curves of kinetics of a relaxation of the atomic order.

Crystal structures of Fe–Ni alloys in extreme conditions (particularly, such as a state of the Earth’s interior core) at high pressure, p, and temperature, T, are reviewed. A role of magnetic effects in atomic ordering, interplay between the atomic and magnetic orders, and pressure effects on magnetic properties of Fe–Ni alloys (Curie temperature,...

Using the self-consistent field approximation, the static concentration waves approach and the Onsager-type kinetics equations, the descriptions of both the statistical thermodynamics and the kinetics of an atomic ordering of D019 phase are developed and applied for h.c.p.-Ti–Al alloy. The model of order–disorder phase transformation describes the...

Within the framework of the self-consistent field approximation and the static concentration waves approach, a statistical-thermodynamic description of D019-type superstructure in Ti–Al alloy is developed. A model of order–disorder phase transformation is applied for the non-stoichiometric intermetallic Ti3Al phase. Interatomic-interaction paramete...

Relaxation of diffuse-scattering intensities of various kinds of waves is a phenomenon of an especial interest since its study enables one to obtain the most detailed information on both the equilibrium short-range order (SRO) and the non-equilibrium SRO, and therefore, it is the most convenient instrument for investigating SRO kinetics. The SRO ki...

Using the static concentration waves’ method and self-consistent-field approximation, the Onsager-type kinetics equation is solved to describe the L12-type long-range order (LRO) relaxation. To calculate the diffusivities for Permalloy, the experimental diffraction data in respect to LRO-parameter evolution for Ni3Fe are used. Theoretical curves of...

The statistical-thermodynamics and kinetics models of substitutional atomic order in the two-dimensional graphene-based crystal lattices with stoi¬chiometries of 1/8, 1/4, and 1/2 types are proposed. Impossibility of the stable ordering in the structures with stoichiometries of 1/6 and 1/3 is ascertained (at least, in case of a short-range interact...

The ordering kinetics is studied using available data of measurements of residual electrical resistivity for substitutional f.c.c.-Ni-Al alloys during the isothermal annealing. Within the framework of the first-order and (more realistic) second-order kinetics models, the maximum characteristic relaxation times and equilibrium values of the residual...

One more method of study of the short-range order kinetics of H-atoms over tetrahedral interstices in lutetium (Lu) is proposed. It can be realized by the using of available data of measurements of heat capacity for h.c.p.-Lu–H interstitial solid solutions during the isothermal annealing. Comparison of estimated-parameters data from heat capacity a...

One more method of study of the short-range order kinetics of H-atoms over tetrahedral interstices in lutetium (Lu) is proposed. It can be realized by the using of available data of measurements of heat capacity for h.c.p.-Lu–H interstitial solid solutions during the isothermal annealing. Comparison of estimated-parameters data from heat capacity a...

The ordering kinetics is studied using available data of measurements of residual electrical resistivity for substitutional f.c.c.-Ni–Al alloys during the isothermal annealing. Within the framework of the first-order and (more realistic) second-order kinetics models, the maximum characteristic relaxation times and equilibrium values of the residual...

The microscopic model of atomic diffusion is considered to describe the short-range order relaxation kinetics within the f.c.c.-Ni-Fe Permalloys. The model takes into account both the discrete and anisotropic characters of atomic jumps within the long-range field of concentration heterogeneities of the interacting atoms in an alloy. Experimental da...

The microscopic theory of atomic diffusion kinetics is used for f.c.c. substitutional solid solutions. Within this approach, the short-range order relaxation is due to the atomic migration. Experimental data on the time dependence of radiation diffuse scattering are used for the determination of microscopic characteristics of atomic migration. The...

The time evolution of diffuse X-ray scattering intensities conditioned by the short-range order (SRO) in Ni–11.8 at.% Mo solid solutions is investigated. As shown, the transition from a quenched (nonequilibrium) state to the equilibrium one is accompanied by the complex time reorganization of various SRO types (namely, N2M2, N4M, N2M). Computer sim...

The time evolution of diffuse X-ray scattering intensities conditioned by the short-range order (SRO) in Ni-Mo solid solutions is investigated. As shown, the transition from a quenched (nonequilibrium) state to the equilibrium one is accompanied by the complex time reorganization of various SRO types. Computer simulations of local atomic configurat...

The microscopic theory of atomic diffusion kinetics is used for f.c.c. substitutional solid solutions. Within this approach, the short-range order relaxation is due to the atomic migration. Experimental data on the time dependence of radiation diffuse scattering are used for the determination of microscopic characteristics of atomic migration. The...

The further theoretical study of the short-range order kinetics of H-atoms at tetrahedral interstices in h.c.p. lanthanoids (Ln), for instance, lutetium (Lu), is developed. It is studied by the use of available data of measurements of residual electrical resistivity for interstitial solid solutions h.c.p.-Lu-H during the isothermal annealing. Withi...

As a result of study of the relaxation of intensity of a diffuse scattering of X-rays bound with the short-range order of a binary f.c.c. alloy, the Fourier components of probabilities of jumps of atoms of both components are defined within the framework of kinetic models of the first and second orders (and determined on an example of solid solutio...

I. Микроскопические параметры миграции атомов в ГЦК-Ni—Mo в Фурье-представлении Изучена кинетика остаточного электросопротивления и интенсивности диффузного рассеяния, связанная с релаксацией ближнего порядка атомов в твердом растворе Ni—11,8% ат. Мо. Релаксация ближнего по-рядка включает одновременное протекание разных процессов с отли-чающимися х...

By using quantitative information about the radiation diffuse-scattering intensity of the disordered f.c.c. substitutional alloy Me′1-cMe″c (c—concentration) the Fourier component, w∼k, of mixing energies of Me′ and Me″ atoms may be estimated. We have to use the measurement data of the diffuse-scattering intensities at the corresponding reciprocal-...

Ni та Fe з суттєво різними спінами обумовлює можливість його «переривчастого» фазового переходу з парамагнітного стану в магнітний. Показано, що втілення малих добавок C у сплав заміщення ГЦК-Fe—Ni імовірніше підвищує феромагнітну складову зв'язку спінів Ni зі спінами Fe, понижує феромагнітну складову зв'язку спінів Ni зі спінами Ni і підвищує анти...